Note if I don't do "modprobe loop" command just hangs forever. I would expect either a not supported type error, or for a successful mount. Any ideas as to why it freezes instead? Any ideas what the "No such device" error means? /dev/loop0 exists. I can also tell it is doing something, as if I tell it the wrong filesystem type I get an "Invalid argument" error instead.

Never mind my bad. My first attempt was without loop.ko loaded, hence the freeze. My next attempt was with an iso9660 which is not supported. My third attempt was with what I thought was a fat file, but turned out to be a gzip cpio file. When I finally tried with an ext3 filesystem it worked fine. Looks like I just need to rebuild to add iso9660 support. (I typically mount the iso9660 files as part of my network booting configuration.)

It almost works after recompiling the kernel with the appropriate filesystem, and loading the correct modules, the mount works successfully. The problem is the umount does not seem to work correctly. After umounting all loop filesystems I see: